The present invention relates to a combination clutch and brake unit. More particularly, the present invention relates to a clutch and brake unit in which the frictionally engageable clutch and brake discs are immersed in a bath of oil so that the kinetic energy produced in starting and stopping heavy loads is transmitted by shearing the oil between the various clutch and brake discs.
Dry friction clutch/brakes depend on the rubbing of a dry friction plate against a dry reaction member to start and stop a press. The continuous dry rubbing causes wearing of both the friction plate and the reaction member as well as causing the generation of heat in these members. The faster the press operates and/or the faster the flywheel rotates, the greater is the amount of wear and heat which are generated. The generation of this heat and wear requires periodic gap adjustments between the friction plate and the reaction member to keep the clutch and brake functioning and thus the press operating correctly. The trip rate or cycle speed of a press equipped with a dry friction brakeand clutch is limited because the mass of the unit determines its heat dissipation capacity. If the mass of the unit is increased to increase its heat capacity, the inertia that must be started and stopped is also increased. These factors define a closed loop from which it is impossible to escape when trying to substantially increase the performance of the system.
Oil shear brake and clutch units have been developed to eliminate the problems associated with the dry friction type of units. Properly designed oil shear brake and clutch units offer the advantage of little or no wear of the friction plates in the disc stacks and they do not produce brake fade. This provides a more precise operation of the press and dramatically increases press up-time. The oil film between the adjacent discs carries the heat generated by the start-stops of the unit away from the disc stacks. The oil provided to the brake and clutch units can be continuously circulated through the units and through a cleaning and cooling system or the oil can be kept within a sump located within the drive. Both systems ensure the consistent removal of the generated heat. This removal of heat offers the advantage that there is now no practical limit for the press trip rate and/or the rotational speed of the flywheel.
While these oil shear clutch and brake units have met with considerable success as drive units for presses, the continued development of these drive units includes the development of oil supply systems for ensuring a continuous supply of oil to the clutch discs as well as air circulation systems which direct air over the outer surface of the drive to assist in the cooling of the oil.
The present invention provides the art with a press drive system which uses an oil shear brake and an oil shear clutch. The brake and clutch units each use a disc stack of multiple discs. Cooling and lubrication oil is supplied to the disc stacks through a central bore in the output shaft and through a plurality of radial bores extending through the output shaft and opening to the inner diameter of the disc stacks. An oil cup is secured to the input shaft in order to guide the cooling and lubricating oil to the central bore in the output shaft. In addition, a unique shroud and fan design located adjacent the input end of the drive unit provides a continuous flow of air over the unit in order to increase the cooling for the oil and drive unit.
Other advantages and objects of the present invention will become apparent to those skilled in the art from the subsequent detailed description, appended claims and drawings.